Clostridium perfringens is a pathogenic bacterium responsible for a variety of disorders, including necrotic enteritis, gas gangrene and food poisoning. C. perfringens is predominantly a soil organism. C. perfringens is an important pathogenic anaerobe.
There are several habitats in the body (for example, in the intestinal tract and the oral cavity) that are generally anaerobic, and in which obligately anaerobic bacteria can be found as part of the normal flora. However, other parts of the body can become anaerobic as a result of tissue injury or trauma, which results in reduction of blood supply to the injured site, and such anaerobic sites can then become available for colonisation by obligate anaerobes, such as C. perfringens. 
The presence of C. perfringens in the intestinal tract of an animal can result in necrotic enteritis, food poisoning and growth retardation, for example. In particular, the presence of C. perfringens in the intestinal tract of poultry, in particular broiler chickens, has been linked with various conditions, such as gut lesions and necrotic enteritis, and can result in a significant reduction in the growth of poultry.
In addition, C. perfringens is a causative agent of gas gangrene, which can occur as a result of tissue injury or trauma and thus an anaerobic environment, which is suitable for colonisation by obligate anaerobes, such as C. perfringens. 
Like viruses in general, bacteriophages can be divided into those with RNA genomes (mostly small and single stranded), those with small DNA genomes (generally less than 10 kb, mostly single stranded) and those with medium to large DNA genomes (30-200 kb).
The genes in bacteriophages are clustered into early stage and late stage genes.
In virulent phages, the genes whose products are needed for phage DNA synthesis and host DNA breakdown, including those mediating nucleotide metabolism and the proteins that make up the replication complex, are all expressed immediately after infection. With time, early synthesis is shut off and other genes that code for virion components and lysis genes are activated. The shutoff of early genes is effected both at the transcriptional and the translational level.
In temperate phages, the phage may undergo lysogeny, wherein genes are switched on upon infection which cause integration of the phage into the host genome such that the phage is propagated indirectly by this means. The lysogenic state, once established, is quite stable. Environmental events that harm the lysogenic bacterial host can cause the lysogenic state to break down and can trigger the lytic life cycle of the integrated phage. At which point, the phage switches to gene (both early and late) which cause the lytic life cycle.
Once the late genes are expressed in both virulent and temperate phages, the stage is set for assembling virions. The heads, tails, tail fibres and soluble protein catalysing tail fibre addition are all made separately. The heads and tails typically combine first to form complexes and finally tail fibres are added to the complex.
The final stage of the cycle is cellular lysis, releasing virions into the medium. Lysis usually requires two gene products: a lysin, which attacks the bonds joining N-acetylglucosamines in the rigid murein layer; and a holin, which creates holes in the inner membrane, allowing the lysin to reach its substrate.
Thus, bacteriophage lysins are phage-encoded cell wall hydrolysing enzymes which are synthesised during late gene expression in the lytic cycle of phage multiplication and mediate the release of progeny virions from infected cells through degradation of the bacterial peptidoglycan.
EP 0 510 907 discloses a lysin from phages of Listeria monocytogenes and formulations of such a lysin substantially free of the bacteriophage itself, together with a method of destroying L. monocytogenes. Although EP 0 510 907 also suggests the use of a lysin from phages of Clostridium tyrobutyricum, the specification does not show how to obtain such an isolated lysin nor the sequence thereof.
WO00/11472 teaches a detection method using cell wall binding domains of proteins and/or enzymes.
Prior to the present invention the lytic cycle of bacteriophages that infect C. perfringens have been little studied.
The term “bacteriophage” as used herein is to be regarded as being interchangeable with the term “phage”.